The field of rapid diagnostic testing has evolved for many years to permit the detection of analytes in a variety of sample types. The use of polyclonal antibodies was followed by the use of monoclonal antibodies to generate assays with high specificity for a number of analytes, including hormones, blood cells, drugs and their metabolites, as well as the antigens of infectious agents including Strep A, Strep B, Chlamydia, HIV, RSV, influenza A and influenza B and many others. The visible signal generated by enzyme-catalyzed reactions or by the accumulation of a visible signal at the level of a test line has also resulted in rapid development of highly sensitive results. Many of the rapid immunoassay-based tests include a solid housing encasing a test strip. However, recently, immunochromatographic assays have been manufactured which do not have solid housings. Such tests, referred to as dipsticks, can be dipped directly into a tube containing a pre-determined amount of the liquid sample of interest. The extremity of the dipstick containing a sample-receiving pad is generally brought in contact with a liquid sample, and the liquid migrates up the flow path. Advantages of the dipstick format include ease of use and minimum handling, which reduces the opportunities for contamination and procedural errors, and lowers manufacturing costs.
One disadvantage of current immunochromatographic dipsticks is that they can only detect the presence of a single analyte. Often these devices are limited because there is no provision to mark the location of possible multiple test lines along the flow path. In the field of chemical urinalysis, dipsticks carrying multiple pads, each specific for a urine analyte to be detected and measured, the dipstick is dipped into the urine sample, then removed from the container, blotted to eliminate excess urine, and applied against a template in order to read the results. These devices are capable of evaluating multiple analytes, but are problematic. For example, such devices increase the chances of contamination by carry-over of material from one device to another, with the consequence of potentially inaccurate results. Moreover, this format exposes the user to potential contamination via removing the strip from the urine sample, blotting it on an absorbent paper, which becomes contaminated, applying it against the template, which often is the exterior wall of the product container, thereby contaminating the product package itself. Further, as indicated, an external template is required to read results.
It is recognized in a variety of fields that the use of single analyte rapid tests is often limiting, for example, because only one analyte at a time can be evaluated. The advantage of rapidity is therefore challenged by the limitation of current assays as adjuncts to the diagnosis of a disease state. For instance, the pediatric units have to make differential diagnostics of Flu A, Flu B, RSV and other upper respiratory viruses, on infants that are in need of urgent care. The availability of rapid test panels would greatly facilitate the doctors' efforts to diagnose the condition, and therefore to take the appropriate course of action faster, more easily, and at lower cost. To date, no such assay has been developed that allows the differential diagnostic of two or more analytes on a single test strip, in a minimally involving procedure.
In summary, chemical urinalysis dipstick assays have been used for many years to determine the presence (or amount) of multiple analytes in a urine sample; however, the technology used to perform such assays not only has undesirable use characteristics but is not readily transferable to immunologic based assays (dipstick or lateral flow) which require flow of sample through the assay device rather than immersion of the device (in particular immersion of the test portion of the device) into a sample. For example, with respect to the use of chemical urinalysis dipsticks, the fact that they must be submerged into the urine sample, removed and blotted of excess urine then placed in physical contact (or very close proximity) with an external, typically reusable (and hence contaminable), test results panel (i.e., template) is not just undesirable but unsafe, particularly if the sample contains contagious agents such as virus or bacteria. Further, because immunologic based assays typically employ at least two, generally sequential reactions (for example a labeling followed by a capture (test) reaction), they are not amenable to submersion into a sample in the same manner as the chemical urinalysis dipsticks. Thus, there is a need in the art for devices and methods that addresses these problems in the art. The present invention addresses these and other related needs in the art.